low idle at start up

[arctic86]

I have a 1986 coupe with7400 mile's on her the car run's great but when u first start her up she idle's ruff.
my queston has any one else had this problem and should i take it to the local chevy dearler?

It idle's abought 4 to7 hundred rpm and the whole car shake's then once it warm's up it idles at 9 to 1100.

 

[582Boat]

Low rpm's

I have a 1986 coupe with7400 mile's on her the car run's great but when u first start her up she idle's ruff.
my queston has any one else had this problem and should i take it to the local chevy dearler?

It idle's abought 4 to7 hundred rpm and the whole car shake's then once it warm's up it idles at 9 to 1100.

Had a simular problem when I had a opispark problem, they found some sensor that had to be replaced, can't remember exact.

 

[arctic86]

thank's for the info dr.wells2.

I thought that it might be a sensor also,I'll start looking at those thing's this weekend.
thank's for your help.
p.s.( nice car!)

 

[vetteboy86]

My car will occasionally start up and idle rough. It will idle around 4 to 5 hundred rpm's before going into fast idle. Once in fast idle it runs fine, and comes out of fast idle very nicely. I am not throwing any codes, and if you arent either it will be hard to trace. However after going to the CAC cruise fest i am going to use Chevron Techron from know on. It might help the problem, maybe caused by dirty injectors. Otherwise for what it is worth, i turn the key to the on position for a few seconds before starting.


craig

 

[arctic86]

thank's for the info vetteboy86.

I have a new iac valve on order to see if that's the problem, but you are right i should clean the injectors maybe that's the problem.

If this car wasn't so fun to drive i would get real frustrated:L

thank's for your input.

 

[WhalePirot]

You can adequately clean the injectors simply, by using quality, detergent gasoline.

How does the engine run if you step on the go pedal, during the low idle period? can you 'hold' it at a higher, smooth RPM?

 

[Vettefan87]

If you arent I would try running premium gasoline and two bottles of that Chevron Techron to a tank of gas about every 6,000 miles. Try this and see if you can get lucky before you start replacing sensors.

 

[arctic86]

vettefan87

vettefan87
thank's for the info i guess that would be the cheaper way to start out with!

 

[WhalePirot]

An extra injector was using until '87, I believe, for cold starts. Later models simply had the ECM increase fuel to the other 8 for the same reason.

Can you idle her up with the pedal for smooth cold running?

BTW, my guess is that your IAC is a waste of cash.

 

[arctic86]

whalepirot

whalepirot:
Thank's for the info,when i give it gas at start up when idleing at a higher rpm it does run smooth.
I just tryed a bottle of stp injector cleaner and see what that doe's.
thank's for your help!

 

[WhalePirot]

Sounds like a good start, arctic. It'd be nice if a few tanks of high detergent fuel would clean the injectors up and solve your problem. YW, too. I hope it helps you to the end.

 

[gray85]

My problem seems to relate. Once the 9th injector (cold start) shuts off, the car runs into a idle search pattern and finally locks in. My thought is that the computer can not handle the addition hp modifications. I see a new chip in the Mid American cat, which is a super duper chip for $400. There has to be a way to progam your own chip, instead of spending $400.
I only have the problem after the cold start injector shuts off and untill the idle is locked in, which is about 8min every day. Not a big problem, but it is starting to drive me crazy!

 

[WhalePirot]

I 'd have to try to research to see if the cold injector shutdown coincides with the ECM going close loop. The hunting idle sounds characteristic of a modified engine, running a chip misprogrammed for it. The computer is trying to adjust for the feedback it is getting from the sensors and confused by the mods. Quite a lot has been written in various threads on the subject, but I have little faith in mail order chips.

The last step in modifying an ECM controlled engine is to get the chip programmed for your 'new' engine. Until that step is completed, expect less-than-optimal performance and running characteristics.

A custom chip is ideal, anything else is target practice, IMHO.

 

[gray85]

You hit the nail on the head, I have a mail order chip. I don't believe that the factory or mail order chip is set-up for my modifications.
My understanding is that I need to have a chip programmed for my engine with the appropriate settings (cam, TB size, fuel pressure, fan temp, etc.). Who and where can burn a chip?

 

[WhalePirot]

You might check with SLP in Tom's River. See if they, or a local Vette club that is into performance, can refer you to someone nearby.

Good luck!